U.S. patent application number 11/817449 was filed with the patent office on 2009-01-08 for braking-driving force control device of vehicle.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Satoshi Ando, Yoshinori Maeda, Kazuya Okumura, Koji Sugiyama, Michitaka Tsuchida, Yoshio Uragami, Kensuke Yoshizue.
Application Number | 20090012686 11/817449 |
Document ID | / |
Family ID | 36941270 |
Filed Date | 2009-01-08 |
United States Patent
Application |
20090012686 |
Kind Code |
A1 |
Maeda; Yoshinori ; et
al. |
January 8, 2009 |
Braking-Driving Force Control Device of Vehicle
Abstract
When either one of a vehicle target braking/driving force and a
target yaw moment cannot be achieved by a braking/driving forces of
wheels, a distribution ratio is calculated to be a small value as a
value indicating an acceleration or deceleration operation by a
driver increases, and to be a great value as a value indicating a
steering operation by a driver increases, for example. A straight
line closest to a point of the target braking/driving force and the
target yaw moment is specified, among sides of a quadrangle or
hexagon indicating a range of the braking/driving force and yaw
moment attainable by the braking/driving forces of the wheels in a
rectangular coordinate of the braking/driving force and the vehicle
yaw moment. The value of the coordinate at the target point, which
is an internally dividing point of the straight line based upon the
distribution ratio, is defined as the target braking/driving force
after the modification and the target yaw moment after the
modification, whereby the target braking/driving force and the
target yaw moment are modified with the ratio based upon the
condition of the driving operation by a driver.
Inventors: |
Maeda; Yoshinori;
(Aichi-ken, JP) ; Okumura; Kazuya; (Shizuoka-ken,
JP) ; Tsuchida; Michitaka; (Shizuoka-ken, JP)
; Uragami; Yoshio; (Shizuoka-ken, JP) ; Yoshizue;
Kensuke; (Shizuoka-ken, JP) ; Ando; Satoshi;
(Shizuoka-ken, JP) ; Sugiyama; Koji;
(Shizuoka-Ken, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
TOYOTA-SHI
JP
|
Family ID: |
36941270 |
Appl. No.: |
11/817449 |
Filed: |
February 24, 2006 |
PCT Filed: |
February 24, 2006 |
PCT NO: |
PCT/JP2006/304022 |
371 Date: |
August 30, 2007 |
Current U.S.
Class: |
701/70 |
Current CPC
Class: |
B60T 2201/14 20130101;
B60W 2050/0057 20130101; B60W 10/08 20130101; B60T 2260/08
20130101; B60W 30/02 20130101; B60T 8/1755 20130101; B60W 2520/10
20130101; B60W 2540/10 20130101; B60W 2510/20 20130101; B60W
2540/18 20130101; B60T 8/174 20130101; B60W 2510/182 20130101; B60W
2510/18 20130101; B60W 10/18 20130101; B60T 2270/613 20130101; B60W
10/04 20130101 |
Class at
Publication: |
701/70 |
International
Class: |
B60T 8/1755 20060101
B60T008/1755; B60W 10/04 20060101 B60W010/04; B60W 10/08 20060101
B60W010/08; B60W 10/18 20060101 B60W010/18; B60W 30/02 20060101
B60W030/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2005 |
JP |
2005-056490 |
Claims
1. A vehicle braking/driving force control apparatus comprising:
braking/driving force applying means that can apply braking/driving
forces to wheels; means for detecting an amount of driving
operation by an occupant; means for calculating a vehicle target
braking/driving force and a vehicle target yaw moment, which should
be generated by the braking/driving forces of the wheels, on the
basis of at least the amount of the driving operation by the
occupant; and control means for controlling the braking/driving
force applied to each wheel by the braking/driving force applying
means such that, when said vehicle target braking/driving force
and/or said vehicle target yaw moment cannot be achieved by the
braking/driving forces of the wheels, said target braking/driving
force and/or said target yaw moment is modified to be increased or
decreased to take values attainable by the braking/driving forces
of the wheels, and the vehicle braking/driving force and the yaw
moment by the braking/driving forces of the wheels become said
target braking/driving force after the modification and said target
yaw moment after the modification, wherein said control means is
configured to determine a ratio of the modification to said target
braking/driving force and said target yaw moment on the basis of a
condition of a driving operation by a driver.
2. A vehicle braking/driving force control apparatus according to
claim 1, wherein said control means modifies to decrease said
target braking/driving force and/or said target yaw moment such
that the target braking/driving force after the modification and
the target yaw moment after the modification become the values
attainable by the braking/driving forces of the wheels.
3. A vehicle braking/driving force control apparatus according to
claim 1, wherein said control means determines a straight line,
which is the closest to a point indicating said target
braking/driving force and said target yaw moment, among lines
indicating the maximum values of the magnitude of the vehicle
braking/driving force and the magnitude of the vehicle yaw moment
by the braking/driving forces of the wheels, in a rectangular
coordinate with the vehicle braking/driving force and the vehicle
yaw moment as coordinate axis, sets the value at the target point
as said target braking/driving force after the modification and
said target yaw moment after the modification with an internally
dividing point of said straight line defined as said target point,
and determines the ratio of the interior division of said straight
line on the basis of the condition of the driving operation by a
driver.
4. A vehicle braking/driving force control apparatus according to
claim 1, wherein said control means defines, as the target point,
the internally dividing point of said straight line within the
range where the magnitude of the braking/driving force is not more
than said target braking/driving force, when the magnitude of said
target braking/driving force exceeds the maximum value of the
braking/driving force attainable by the braking/driving forces of
the wheels.
5. A vehicle braking/driving force control apparatus according to
claim 1, wherein said control means defines, as the target point,
the internally dividing point of the straight line within the range
where the magnitude of the yaw moment is not more than said target
yaw moment, when the magnitude of said target yaw moment exceeds
the maximum value of the yaw moment attainable by the
braking/driving forces of the wheels.
6. A vehicle braking/driving force control apparatus according to
claim 1, wherein said condition of the driving operation by a
driver is a condition of an acceleration or deceleration operation,
and a condition of a steering operation.
7. A vehicle braking/driving force control apparatus according to
claim 1, wherein said control means determines the ratio of the
modification by using a neural network to which a value indicating
said condition of the driving operation by a driver is
inputted.
8. A vehicle braking/driving force control apparatus according to
claim 1, wherein said means for calculating a vehicle target
braking/driving force and a vehicle target yaw moment calculates
said vehicle target braking/driving force and vehicle target total
yaw moment for causing the vehicle to stably run on the basis of at
least the amount of the driving operation by an occupant, estimates
a vehicle turning yaw moment due to a lateral force of each wheel
on the basis of at least the amount of the driving operation by the
occupant, and calculates said vehicle target yaw moment by
subtracting said turning yaw moment from said target total yaw
moment.
9. A vehicle braking/driving force control apparatus according to
claim 3, wherein said lines indicating the greatest values of said
vehicle braking/driving force and said vehicle yaw moment are
determined by the greatest value of the vehicle driving force, the
greatest value of the vehicle braking force, the greatest value of
the vehicle yaw moment in the leftward turning direction and the
greatest value of the vehicle yaw moment in the rightward turning
direction.
10. A vehicle braking/driving force control apparatus according to
claim 3, wherein said lines indicating the greatest values of said
vehicle braking/driving force and said vehicle yaw moment are
variably set in accordance with a road friction coefficient.
11. A vehicle braking/driving force control apparatus according to
claim 6, wherein said condition of the acceleration or deceleration
operation is determined on the basis of the amount of the
acceleration operation, the rate of change of the amount of the
acceleration operation, the amount of braking operation, and the
rate of change of the amount of the braking operation.
12. A vehicle braking/driving force control apparatus according to
claim 6, wherein said condition of the steering operation is
determined on the basis of the amount of the steering operation and
the rate of change of the amount of the steering operation.
13. A vehicle braking/driving force control apparatus according to
claim 6, wherein said means for calculating the vehicle target
braking/driving force and the vehicle target yaw moment calculates
a vehicle target longitudinal acceleration and a vehicle target yaw
rate for stably running the vehicle on the basis of at least the
amount of the driving operation by an occupant, and calculates said
vehicle target driving/braking force and the vehicle target total
yaw moment on the basis of said vehicle target longitudinal
acceleration and said vehicle target yaw rate, respectively.
14. A vehicle braking/driving force control apparatus according to
claim 6, wherein said control means calculates the target
braking/driving force of each wheel on the basis of said vehicle
target braking/driving force, said vehicle target yaw moment, and
the distribution ratio of the braking/driving force to the front
and rear wheels, and controls the braking/driving force applied to
each wheel on the basis of the target braking/driving force of each
wheel.
Description
TECHNICAL FIELD
[0001] The present invention relates to a vehicle braking/driving
force control apparatus, and more particularly to a vehicle
braking/driving force control apparatus that controls
braking/driving force of each wheel.
BACKGROUND ART
[0002] As one of braking/driving force control apparatuses for a
vehicle, such as an automobile, there has conventionally been known
a driving force control apparatus, as disclosed in Japanese
Unexamined Patent Application No. HE19-309357 for example, for
performing a distribution control of driving force applied to left
and right wheels so as to exert a required yaw moment to a vehicle.
Further, there has already been known a braking force control
apparatus that controls a vehicle braking/driving force and yaw
moment by controlling braking forces of wheels so as to secure a
vehicle running stability. This braking/driving force control
apparatus can enhance running stability of a vehicle.
[0003] In general, the vehicle braking/driving force and yaw moment
can be controlled through the control of the braking/driving forces
of the wheels. However, there is a limitation in the
braking/driving force that can be generated by each wheel.
Therefore, there may be the case in which the braking/driving force
and/or yaw moment required to the vehicle exceeds the value
attainable by the control of the braking/driving forces of the
wheels. This situation is not considered in the above-mentioned
conventional braking/driving force control apparatus, and it is
necessary to make an improvement on this point.
DISCLOSURE OF THE INVENTION
[0004] The present invention had been accomplished in view of the
circumstance described above in the conventional vehicle
braking/driving force control apparatus that is configured to
control braking/driving force and yaw moment of the vehicle through
the control of the braking/driving forces of wheels, and the main
subject of the present invention is to achieve a braking/driving
force and yaw moment, which are as closer to the braking/driving
force and the yaw moment required to the vehicle as possible and
are suitable for the condition of a driving operation by a driver,
within the ranges of the braking/driving forces that can be
generated by the wheels, through the control of the braking/driving
forces of the wheels such that the vehicle braking/driving force
and the yaw moment become values, which are as closer to the
braking/driving force and yaw moment required to the vehicle and
are suitable for the condition of the driving operation by a
driver, within the ranges of the braking/driving forces that can be
generated by the wheels.
[0005] The above-mentioned main subject can be achieved by a
vehicle braking/driving force control apparatus comprising
braking/driving force applying means that can apply braking/driving
forces to wheels; means for detecting an amount of driving
operation by an occupant; means for calculating a vehicle target
braking/driving force and a vehicle target yaw moment, which should
be generated by the braking/driving forces of the wheels, on the
basis of at least the amount of the driving operation by the
occupant; and control means for controlling the braking/driving
force applied to each wheel by the braking/driving force applying
means such that, when the vehicle target braking/driving force
and/or the vehicle target yaw moment cannot be achieved by the
braking/driving forces of the wheels, the target braking/driving
force and/or the target yaw moment is modified be increased or
decreased to take values attainable by the braking/driving forces
of the wheels, and the vehicle braking/driving force and the yaw
moment by the braking/driving forces of the wheels become the
target braking/driving force after the modification and the target
yaw moment after the modification, wherein the control means is
configured to determine a ratio of the modification to the target
braking/driving force and the target yaw moment on the basis of the
condition of the driving operation by a driver.
[0006] According to this configuration, even in case where the
target braking/driving force and/or the target yaw moment cannot be
achieved by the braking/driving forces of the wheels, a
braking/driving force and yaw moment, which are as closer to the
braking/driving force and the yaw moment required to the vehicle as
possible and suitable for the condition of the driving operation by
a driver, can be achieved within the range of the braking/driving
forces that can be generated by the wheels.
[0007] In the above-mentioned configuration, the control means may
modifies to decrease the target braking/driving force and/or the
target yaw moment such that the target braking/driving force after
the modification and the target yaw moment after the modification
become the values attainable by the braking/driving forces of the
wheels.
[0008] According to this configuration, it can surely be prevented
that the magnitude of the target braking/driving force and/or the
magnitude of the target yaw moment excessively increases.
[0009] In the above-described configuration, the control means may
determine a straight line, which is the closest to a point
indicating the target braking/driving force and the target yaw
moment, among lines indicating the maximum values of the magnitude
of the vehicle braking/driving force and the magnitude of the
vehicle yaw moment by the braking/driving forces of the wheels, in
a rectangular coordinate with the vehicle braking/driving force and
the vehicle yaw moment as coordinate axis, set the value at the
target point as the target braking/driving force after the
modification and the target yaw moment after the modification with
an internally dividing point of the straight line defined as the
target point, and determine the ratio of the interior division of
the straight line on the basis of the condition of the driving
operation by a driver.
[0010] According to this configuration, the target braking/driving
force after the modification and the target yaw moment after the
modification can be set to the values that are as closer to the
braking/driving force and yaw moment required to the vehicle as
possible and suitable for the condition of the driving operation by
a driver.
[0011] In the above-mentioned configuration, the control means may
define, as the target point, the internally dividing point of the
straight line within the range where the magnitude of the
braking/driving force is not more than the target braking/driving
force, when the magnitude of the target braking/driving force
exceeds the maximum value of the braking/driving force attainable
by the braking/driving forces of the wheels.
[0012] This configuration can surely prevent that the magnitude of
the target braking/driving force excessively increases, and achieve
that the target braking/driving force after the modification and
the target yaw moment after the modification become the values that
are as closer to the braking/driving force and yaw moment required
to the vehicle as possible and suitable for the condition of the
driving operation by a driver.
[0013] In the above-mentioned configuration, the control means may
define, as the target point, the internally dividing point of the
straight line within the range where the magnitude of the yaw
moment is not more than the target yaw moment, when the magnitude
of the target yaw moment exceeds the maximum value of the yaw
moment attainable by the braking/driving forces of the wheels.
[0014] This configuration can surely prevent that the magnitude of
the target yaw moment excessively increases, and achieve that the
target braking/driving force after the modification and the target
yaw moment after the modification become the values that are as
closer to the braking/driving force and yaw moment required to the
vehicle as possible and suitable for the condition of the driving
operation by a driver.
[0015] In the above-mentioned configuration, the condition of the
driving operation by a driver may be a condition of an acceleration
or deceleration operation, and a condition of a steering
operation.
[0016] This configuration can achieve that the target
braking/driving force after the modification and the target yaw
moment after the modification become the values that are as closer
to the braking/driving force and yaw moment required to the vehicle
as possible and suitable for the condition of the driving operation
by a driver, according to the acceleration or deceleration
operation and steering operation by a driver.
[0017] In the above-mentioned configuration, the control means may
determine the ratio of the modification by using a neural network
to which a value indicating the condition of the driving operation
by a driver is inputted.
[0018] According to this configuration, the ratio of the
modification can easily and surely be determined to a value
according to the acceleration or deceleration operation and the
steering operation by a driver.
[0019] In the above-mentioned configuration, the means for
calculating a vehicle target braking/driving force and a vehicle
target yaw moment may calculate the vehicle target braking/driving
force and the vehicle target total yaw moment for causing the
vehicle to stably run on the basis of at least the amount of the
driving operation by an occupant, estimate a vehicle turning yaw
moment due to a lateral force of each wheel on the basis of at
least the amount of the driving operation by the occupant, and
calculate the vehicle target yaw moment by subtracting the turning
yaw moment from the target total yaw moment.
[0020] With this configuration, the vehicle target braking/driving
force and the vehicle target yaw moment that should be generated by
the braking/driving forces of the wheels can be surely and
correctly calculated in just proportion on the basis of at least
the amount of the driving operation by an occupant.
[0021] In the above-mentioned configurations, the lines indicating
the greatest values of the vehicle braking/driving force and the
vehicle yaw moment may be determined by the greatest value of the
vehicle driving force, the greatest value of the vehicle braking
force, the greatest value of the vehicle yaw moment in the leftward
turning direction and the greatest value of the vehicle yaw moment
in the rightward turning direction.
[0022] In the above-mentioned configurations, the lines indicating
the greatest values of the vehicle braking/driving force and the
vehicle yaw moment may be variably set in accordance with a road
friction coefficient.
[0023] In the above-mentioned configuration, the condition of the
acceleration or deceleration operation may be determined on the
basis of the amount of the acceleration operation, the rate of
change of the amount of the acceleration operation, the amount of
braking operation, and the rate of change of the amount of the
braking operation.
[0024] In the above-mentioned configuration, the condition of the
steering operation may be determined on the basis of the amount of
the steering operation and the rate of change of the amount of the
steering operation.
[0025] In the above-mentioned configurations, the means for
calculating the vehicle target braking/driving force and the
vehicle target yaw moment may calculate a vehicle target
longitudinal acceleration and a vehicle target yaw rate for stably
running the vehicle on the basis of at least the amount of the
driving operation by an occupant, and calculate the vehicle target
driving/braking force and the vehicle target total yaw moment on
the basis of the vehicle target longitudinal acceleration and the
vehicle target yaw rate, respectively.
[0026] In the above-mentioned configurations, the control means may
calculate the target braking/driving force of each wheel on the
basis of the vehicle target braking/driving force, the vehicle
target yaw moment, and the distribution ratio of the
braking/driving force to the front and rear wheels, and control the
braking/driving force applied to each wheel on the basis of the
target braking/driving force of each wheel.
[0027] In the above-mentioned configurations, depending upon the
values of the vehicle target braking/driving force and/or the
target yaw moment, the vehicle target braking/driving force and/or
the target yaw moment may not be modified to be increased or
decreased with the ratio of the modification, but the vehicle
target braking/driving force after the modification and the vehicle
target yaw moment after the modification may be set to a specific
value attainable by the braking/driving forces of the wheels.
[0028] In the above-mentioned configurations, the braking/driving
force applying means may comprise means for applying driving force
to each wheel independently, and means for applying braking force
to each wheel independently.
[0029] In the above-mentioned configurations, the braking/driving
force applying means may comprise means for applying common driving
force to the right and left wheels, means for controlling the
distribution of the driving force to the right and left wheels, and
means for applying braking force to each wheel independently.
[0030] In the above-mentioned configurations, the means for
applying driving force may comprise means for applying common
driving force to the right and left front wheels, and means for
applying common driving force to the right and left rear
wheels.
[0031] In the above-mentioned configurations, the means for
applying driving force may comprise means for applying common
driving force to the right and left front wheels and the right and
left rear wheels, means for controlling the distribution of the
driving force to the front and rear wheels, means for controlling
the distribution of the driving force to the right and left front
wheels, and means for controlling the distribution of the driving
force to the right and left rear wheels.
[0032] In the above-mentioned configurations, the means for
applying driving force may comprise an electric motor
generator.
[0033] In the above-mentioned configurations, the electric motor
generator may perform regenerative braking upon the braking.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a schematic block diagram showing a
braking/driving force control apparatus applied to a
four-wheel-drive vehicle of a wheel-in-motor type according to a
first embodiment of the present invention;
[0035] FIG. 2 is an explanatory view for explaining various cases
of the relationship between braking/driving force of each wheel and
vehicle braking/driving force and the relationship between
braking/driving force of each wheel and yaw moment;
[0036] FIG. 3 is a flowchart showing a braking/driving force
control routine executed by an electronic controller for
controlling driving force in the first embodiment;
[0037] FIG. 4A is a graph showing the range, that can be achieved
by the braking/driving force of each wheel, of the vehicle
braking/driving force and vehicle yaw moment;
[0038] FIG. 4B is an explanatory view showing the range, that can
be achieved by the control of the braking/driving force of each
wheel, of the vehicle target braking/driving force Fvn and the
vehicle target yaw moment Mvn in the vehicle having a driving
source provided only at the right and left front wheels or at the
right and left rear wheels in the first embodiment;
[0039] FIG. 5 is an explanatory view for showing, in the first
embodiment, a manner of specifying a straight line L, which is the
closest to a vehicle target braking/driving force Fvn and vehicle
target yaw moment Mvn, when a vehicle target braking/driving force
Fvn and a vehicle target yaw moment Mvn are outside the range
attainable by the control of the braking/driving forces of the
wheels, and a manner of setting the coordinate of an internally
dividing point Q of the straight line L to a vehicle target
braking/driving force Fvt after the modification and a vehicle
target yaw moment Mvt after the modification;
[0040] FIG. 6 is an explanatory view showing a neural network to
which a value indicating a condition of an acceleration or
deceleration operation by a driver and a value indicating a
condition of a steering operation by a driver are inputted, and
which outputs a distribution ratio K for calculating the vehicle
target braking/driving force Fvt after the modification and the
vehicle target yaw moment Mvt after the modification;
[0041] FIG. 7 is a schematic block diagram showing a vehicle
braking/driving force control apparatus applied to a
four-wheel-drive vehicle in which driving force and regenerative
braking force from a single electric motor generator, which is
common to four wheels, are controlled so as to be distributed to
the four wheels according to a second embodiment of the present
invention;
[0042] FIG. 8 is an explanatory view for explaining various cases
of the relationship between braking/driving force of each wheel and
vehicle braking/driving force and the relationship between
braking/driving force of each wheel and vehicle yaw moment in the
second embodiment;
[0043] FIG. 9 is an explanatory view for explaining other various
cases of the relationship between braking/driving force of each
wheel and vehicle braking/driving force and the relationship
between braking/driving force of each wheel and vehicle yaw moment
in the second embodiment;
[0044] FIG. 10 is a flowchart showing a braking/driving force
control routine executed by the electronic controller for
controlling driving force in the second embodiment;
[0045] FIG. 11A is a graph showing the range, that can be achieved
by the braking/driving force of each wheel, of the vehicle
braking/driving force and vehicle yaw moment according to the
second embodiment;
[0046] FIG. 11B is an explanatory view showing the range, that can
be achieved by the control of the braking/driving force of each
wheel, of the vehicle target braking/driving force Fvn and the
vehicle target yaw moment Mvn in the vehicle having a driving
source provided only at the right and left front wheels or at the
right and left rear wheels in the second embodiment;
[0047] FIG. 12 is an explanatory view for showing, in the second
embodiment, a manner of specifying a straight line L1, which is the
closest to a vehicle target braking/driving force Fvn and vehicle
target yaw moment Mvn, when a vehicle target braking/driving force
Fvn and a vehicle target yaw moment Mvn are outside the range
attainable by the control of the braking/driving force of the
wheels, and a manner of setting the coordinate of an internally
dividing point Q1 of the straight line L1 to a vehicle target
braking/driving force Fvt after the modification and a vehicle
target yaw moment Mvt after the modification;
[0048] FIG. 13 is an explanatory view for showing, in the second
embodiment, a manner of specifying a straight line L2, which is the
closest to a vehicle target braking/driving force Fvn and vehicle
target yaw moment Mvn, when a vehicle target braking/driving force
Fvn and a vehicle target yaw moment Mvn are outside the range
attainable by the control of the braking/driving forces of the
wheels, and a manner of setting the coordinate of an internally
dividing point Q2 of the straight line L2 to a vehicle target
braking/driving force Fvt after the modification and a vehicle
target yaw moment Mvt after the modification;
[0049] FIG. 14 is a flowchart showing an main part of a
braking/driving force control routine in a third embodiment of a
vehicle braking/driving force control apparatus that is applied to
a four-wheel-drive vehicle of a wheel-in-motor type and is made as
an modified example of the first embodiment;
[0050] FIG. 15 is an explanatory view showing areas S1 to S4 where
the calculation of the vehicle target braking/driving force Fvt
after the modification and the vehicle target yaw moment Mvt after
the modification by the internally dividing point R of the straight
line L on the basis of the distribution ratio K is not executed,
when the vehicle target braking/driving force Fvn and the vehicle
target yaw moment Mvn are outside the range attainable by the
control of the braking/driving forces of the wheels in the third
embodiment;
[0051] FIG. 16 is a flowchart showing an main part of a
braking/driving force control routine in a fourth embodiment of a
vehicle braking/driving force control apparatus that is applied to
a four-wheel-drive vehicle, in which driving force and regenerative
braking force from a single electric motor generator that is common
to four wheels are controlled so as to be distributed to front and
rear wheels and right and left wheels and is made as an modified
example of the second embodiment;
[0052] FIG. 17 is an explanatory view showing areas S1 to S6 where
the calculation of the vehicle target braking/driving force Fvt
after the modification and the vehicle target yaw moment Mvt after
the modification by the internally dividing point R1 or R2 of the
straight line L1 or L2 on the basis of the distribution ratio K is
not executed, when the vehicle target braking/driving force Fvn and
the vehicle target yaw moment Mvn are outside the range attainable
by the control of the braking/driving forces of the wheels in the
third embodiment; and
[0053] FIG. 18 is an explanatory view showing an modified example
in which the vehicle target braking/driving force Fvt and the
vehicle target yaw moment Mvt are calculated within the range not
more than the vehicle target braking/driving force Fvn and/or the
vehicle target yaw moment Mvn.
BEST MODE FOR CARRYING OUT THE INVENTION
[0054] Some preferred embodiments of the present invention will be
explained in detail with reference to the accompanying
drawings.
First Embodiment
[0055] FIG. 1 is a schematic block diagram showing a
braking/driving force control apparatus applied to a
four-wheel-drive vehicle of a wheel-in-motor type according to a
first embodiment of the present invention.
[0056] In FIG. 1, numerals 10FL and 10FR respectively represent
left and right front wheels that are steering wheels, and numerals
10RL and 10RR respectively represent left and right rear wheels
that are non-steering wheels. Electric motor generators 12FL and
12FR that are in-wheel motors are incorporated into the left and
right front wheels 10FL and 10FR respectively, whereby the left and
right front wheels 10FL and 10FR are driven by the electric motor
generators 12FL and 12FR. The electric motor generators 12FL and
12FR also function as regenerative electric generators for each of
the left and right front wheels upon the braking, so that they
generate regenerative braking force.
[0057] Similarly, electric motor generators 12RL and 12RR that are
in-wheel motors are incorporated into the left and right rear
wheels 10RL and 10RR respectively, whereby the left and right front
wheels 10RL and 10RR are driven by the electric motor generators
12RL and 12RR. The electric motor generators 12RL and 12RR also
function as regenerative electric generators for each of the left
and right rear wheels upon the braking, so that they generate
regenerative braking force.
[0058] The driving force from each of the electric motor generators
12FL to 12RR is controlled by an electronic controller 16 for
controlling driving force on the basis of an accelerator opening
.phi. that is a step-on amount of an accelerator pedal, that is not
shown in FIG. 1, detected by an accelerator opening sensor 14. The
regenerative braking force from each of the electric motor
generators 12FL to 12RR is also controlled by the electronic
controller 16 for controlling driving force.
[0059] Although not shown in FIG. 1 in detail, the electronic
controller 16 for controlling driving force is composed of a
microcomputer and a driving circuit, wherein the microcomputer may
have a general configuration to include, for example, a CPU, ROM,
RAM, and input/output port device, those of which are
interconnected with one another via a bi-directional common bus. In
a normal running, electric power charged in a battery, which is not
shown in FIG. 1, is supplied to each of the electric motor
generators 12FL to 12RR, and upon the deceleration and braking of
the vehicle, the electric power generated by the regenerative
braking by each of the electric motor generators 12FL to 12RR is
charged to the battery via the driving circuit.
[0060] The friction braking forces of the left and right front
wheels 10FL and 10FR and the left and right rear wheels 10RL and
10RR are controlled by controlling braking pressures of
corresponding wheel cylinders 22FL, 22FR, 22RL and 22RR by a
hydraulic circuit 20 in a friction braking device 18. Although not
shown in the figure, the hydraulic circuit 20 includes a reservoir,
oil pump, and other various valve devices. In a normal situation,
the braking pressure of each wheel cylinder is controlled in
accordance with the step-on amount of the brake pedal 24 by a
driver and the pressure of a master cylinder 26 that is driven in
accordance with the step-on operation of the brake pedal 24. It is
controlled as necessary through the control of the oil pump or
various valve devices by an electronic controller 28 for
controlling braking force, regardless of the step-on amount of the
brake pedal 24 by a driver.
[0061] Although not shown in FIG. 1 in detail, the electronic
controller 18 for controlling braking force is also composed of a
microcomputer and a driving circuit, wherein the microcomputer may
have a general configuration to include, for example, a CPU, ROM,
RAM, and input/output port device, those of which are
interconnected with one another via a bi-directional common
bus.
[0062] Inputted to the electronic controller 16 for controlling
driving force are a signal indicating a road friction coefficient
.mu. from a .mu. sensor 30; a signal indicating a steering angle
.theta. from a steering angle sensor 32; and a signal indicating a
vehicle speed V from a vehicle speed sensor 34, in addition to the
signal indicating the accelerator opening .phi. from the
accelerator opening sensor 14. Inputted to the electronic
controller 28 for controlling braking force are a signal indicating
a master cylinder pressure Pm from a pressure sensor 36 and signals
indicating braking pressures (wheel cylinder pressures) Pbi (i=fl,
fr, rl, rr) of corresponding wheels from pressure sensors 38FL to
38RR. The electronic controller 16 for controlling driving force
and the electronic controller 28 for controlling braking force
exchange signals with each other according to need. Note that the
steering angle sensor 32 detects a steering angle .theta. with the
leftward turning direction of the vehicle defined as a
positive.
[0063] The electronic controller 16 for controlling driving force
calculates a vehicle target longitudinal acceleration Gxt on the
basis of the accelerator opening .phi. and the master cylinder
pressure Pm, which indicate an amount of acceleration/deceleration
operation by a driver, and calculates a target yaw rate .gamma.t of
the vehicle on the basis of the steering angle .theta., which is an
amount of steering operation by a driver, and the vehicle speed V
through a manner well-known in this technical field. Then, the
electronic controller 16 for controlling driving force calculates a
target braking/driving force Fvn that is required to the vehicle on
the basis of the vehicle target longitudinal acceleration Gxt, and
calculates a target total yaw moment Mvnt required to the vehicle
on the basis of the vehicle target yaw rate .gamma.t.
[0064] The electronic controller 16 for controlling driving force
calculates the vehicle slip angle .beta. with a manner well-known
in this technical field, calculates the slip angle .alpha. of the
left and right front wheels on the basis of the vehicle slip angle
.beta. and the steering angle .theta., and calculates a vehicle
turning yaw moment Ms due to a lateral force of each wheel on the
basis of the slip angle .alpha.. Then, the electronic controller 16
for controlling driving force calculates the value obtained by
subtracting the turning yaw moment Ms from the vehicle target total
yaw moment Mvnt as the vehicle target yaw moment Mvn, required to
the vehicle, through the control of the braking/driving force of
each wheel.
[0065] The electronic controller 16 for controlling driving force
further calculates the vehicle maximum driving force Fvdmax and the
vehicle maximum braking force Fvbmax attainable by the
braking/driving forces of the wheels on the basis of the road
friction coefficient .mu., and calculates the vehicle maximum yaw
moment Mvlmax in the leftward turning direction and the vehicle
maximum yaw moment Mvrmax in the rightward turning direction
attainable by the braking/driving forces of the wheels on the basis
of the road friction coefficient .mu..
[0066] As shown in FIG. 2A, supposing that the vertical load and
the friction coefficients to the road surface of the wheels are the
same, and the sizes of the friction circles of the wheels are the
same, the vehicle maximum driving force Fvdmax under the condition
where the yaw moment by the braking/driving forces of the wheels is
not acted on the vehicle is achieved when the braking/driving
forces Fwxfl and Fwxfr of the left and right front wheels 10FL and
10FR are the maximum driving forces Fwdflmax and Fwdformax and the
braking/driving forces Fwxrl and Fwxrr of the left and right rear
wheels 10RL and 10RR are the maximum driving forces Fwdrlmax and
Fwdrrmax. Similarly, as shown in FIG. 2B, the vehicle maximum
braking force Fvbmax under the condition where the yaw moment by
the braking/driving forces of the wheels is not acted on the
vehicle is achieved when the braking/driving forces Fwxfl and Fwxfr
of the left and right front wheels 10FL and 10FR are the maximum
braking forces Fwbflmax and Fwbformax and the braking/driving
forces Fwxrl and Fwxrr of the left and right rear wheels 10RL and
10RR are the maximum braking forces Fwbrlmax and Fwbrrmax.
[0067] As shown in FIG. 2C, the vehicle maximum yaw moment Mvlmax
in the leftward turning direction under the condition where the
longitudinal force by the braking/driving forces of the wheels is
not acted on the vehicle is achieved when the braking/driving
forces Fwxfl and Fwxrl of the front left and rear left wheels 10FL
and 10RL are the maximum braking forces Fwbflmax and Fwbrlmax and
the braking/driving forces Fwxfr and Fwxrr of the front right and
rear right wheels 10FR and 10RR are the maximum driving forces
Fwdformax and Fwdrrmax. Similarly, as shown in FIG. 2D, the vehicle
maximum yaw moment Mvrmax in the rightward turning direction under
the condition where the longitudinal force by the braking/driving
forces of the wheels is not acted on the vehicle is achieved when
the braking/driving forces Fwxfl and Fwxrl of the front left and
rear left wheels 10FL and 10RL are the maximum driving forces
Fwdflmax and Fwdrlmax and the braking/driving forces Fwxfr and
Fwxrr of the front right and rear right wheels 10FR and 10RR are
the maximum braking forces Fwbformax and Fwbrrmax.
[0068] In case where the output torque of each of the electric
motor generators 12FL to 12RR is sufficiently great, the maximum
driving force and the maximum braking force of each wheel are
determined by the road friction coefficient .mu., so that, with the
vehicle accelerating direction and vehicle leftward turning
direction defined as positive, the following relationships are
established between the maximum driving force and the maximum
braking force of each wheel, the vehicle maximum driving force and
the vehicle maximum braking force, and the vehicle maximum yaw
moment in the leftward turning direction and the vehicle maximum
yaw moment in the rightward turning direction.
Fwdflmax=Fwdformax=-Fwbflmax=-Fwbformax
Fwdrlmax=Fwdrrmax=-Fwbrlmax=-Fwbrrmax
Fvdmax=-Fvbmax
Mvimax=-Mvrmax
[0069] Since the maximum driving force Fwdimax and the maximum
braking force Fwbimax (i=fl, fr, rl, rr) of each wheel are
determined by the road friction coefficient .mu., the vehicle
maximum driving force Fvdmax, vehicle maximum braking force Fvbmax,
vehicle maximum yaw moment Mvimax in the leftward turning
direction, and vehicle maximum yaw moment Mvrmax in the rightward
turning direction are also determined by the road friction
coefficient .mu.. Accordingly, if the road friction coefficient
.mu. is found, the vehicle maximum driving force Fvdmax and the
other aforesaid values can be estimated.
[0070] As shown in FIG. 4A, in a rectangular coordinate with the
vehicle braking/driving force Fvx as abscissa and the vehicle yaw
moment Mv as ordinate, the vehicle braking/driving force Fvx and
the vehicle yaw moment Mv that can be achieved by the control of
the braking/driving force of each wheel take values within a
diamond quadrangle 100 decided by the vehicle maximum driving force
Fvdmax, vehicle maximum braking force Fvbmax, vehicle maximum yaw
moment Mvimax in the leftward turning direction, and vehicle
maximum yaw moment Mvrmax in the rightward turning direction.
[0071] Notably, in FIG. 4, points A to D correspond to the cases A
to D in FIG. 2, wherein the coordinates at the points A to D are
(Fvdmax, 0), (Fvbmax, 0), (0, Mvimax), and (0, Mvrmax),
respectively. As shown by a broken line in FIG. 4A, the quadrangle
100 becomes small as the road friction coefficient .mu. decreases.
Further, as the steering angle .theta. increases, the lateral force
of front left and front right wheels, that are steering wheels,
increases, so that the allowance of the longitudinal force becomes
small. Therefore, the quadrangle 100 becomes small as the magnitude
of the steering angle .theta. increases.
[0072] Supposing that the longitudinal distribution ratio of the
vehicle braking/driving force Fv to the rear wheels is defined as
Kr (constant of 0<Kr<1), and the vehicle tread is defined as
Tr, the following equations 1 to 3 are established. Accordingly,
the electronic controller 16 for controlling driving force sets the
vehicle target braking/driving force Fvt and the vehicle target yaw
moment Mvt by the control of the braking/driving forces of each
wheel to the target braking/driving force Fvn and the vehicle
target yaw moment Mvn, when the vehicle target braking/driving
force Fvn and the vehicle target yaw moment Mvn are within the
above-mentioned quadrangle 100. For example, it calculates the
values satisfying the following equations 1 to 3 as the target
braking/driving forces Fwxti (i=fl, fr, rl, rr) of the wheels by
the least square method.
Fwxfl+Fwxfr+Fwxrl+Fwxrr=Fvt (1)
{Fwxfr+Fwxrr-(Fwxfl+Fwxrl)}Tr/2=Mvt (2)
(Fwxfl+Fwxfr)Kr=(Fwxrl+Fwxrr)(1-Kr) (3)
[0073] When the vehicle target braking/driving force Fvn and the
vehicle target yaw moment Mvn are outside the range of the
above-mentioned quadrangle 100, the electronic controller 16 for
controlling driving force specifies a straight line L of the outer
line of the quadrangle 100, which is the closest to a point P
indicating the vehicle target braking/driving force Fvn and the
vehicle target yaw moment Mvn, calculates a distribution ratio K (a
value greater than 0 and less than 1) for determining an internally
dividing point R of the straight line L by an operation of the
neural network 50 shown in FIG. 6, and defines the braking/driving
force Fv and the yaw moment Mv at the target point R as the vehicle
target braking/driving force Fvt after the modification and the
vehicle target yaw moment Mvt after the modification, with the
internally dividing point R of the straight line L on the basis of
the distribution ratio K employed as the target point R. Then, the
electronic controller 16 for controlling driving force calculates
the values satisfying the foregoing equations 1 to 3 as the target
braking/driving forces Fwxti of the wheels by the least square
method, for example.
[0074] In the illustrated first embodiment, inputted to the neural
network 50 are an acceleration opening .phi., a rate of change of
the acceleration opening .phi.d, a master cylinder pressure Pm, a
rate of change of the master cylinder pressure Pmd, a steering
angle .theta., and a rate of change of the steering angle (steering
angular speed) .phi.d which indicate a condition of a driving
operation by a driver, and the neural network 50 calculates the
distribution ratio K as a weight to the yaw moment. Particularly,
the neural network 50 calculates the distribution ratio K to be a
small value, as the acceleration opening .phi., the rate of change
of the acceleration opening .phi.d, the master cylinder pressure
Pm, and/or the rate of change of the master cylinder pressure Pmd
which indicate a condition of an acceleration or deceleration
operation by a driver are great, while it calculates the
distribution ratio K to be a great value, as the magnitude of the
steering angle .theta. and/or the magnitude of the rate of change
of the steering angle .phi.d which indicate a condition of steering
by a driver are great.
[0075] When the target braking/driving force Fwxti of each wheel
takes a positive value that means it is a driving force, the
electronic controller 16 for controlling driving force sets the
target friction braking force Fwbti and the target regenerative
braking force Fwrti (i=fl, fr, rl, rr) of each wheel to zero,
outputs the signals indicating the target friction braking forces
Fwbti to the electronic controller 28 for controlling braking
force, sets the target driving force Fwdti (i=fl, fr, rl, rr) of
each wheel to the associated target braking/driving force Fwxti,
calculates the target driving currents Iti (i=fl, fr, rl, rr) to
the electric motor generators 12FL to 12RR by unillustrated maps or
functions on the basis of the target driving forces Fwdti, and
controls the driving currents applied to the electric motor
generators 12FL to 12RR on the basis of the target driving currents
Iti, thereby controlling the driving force of each wheel such that
the braking/driving force Fwxi of each wheel becomes the associated
target braking/driving force Fwxti.
[0076] On the other hand, when the target braking/driving forces
Fwxti of each wheel takes a negative value which means that the
target braking/driving force Fwxti is a braking force and the
target braking/driving force Fwxti is not more than the maximum
regenerative braking force of each wheel, the electronic controller
16 for controlling driving force sets the target driving force
Fwdti and the target friction braking force Fwbti of each wheel to
zero, sets the target regenerative braking force Fwrti to the
target braking/driving force Fwxti, and controls the electric motor
generators 12FL to 12RR such that the regenerative braking force
becomes the target regenerative braking force Fwrti.
[0077] When the target braking/driving force Fwxti of each wheel
takes a negative value which means that the target braking/driving
force Fwxti is a braking force and the target braking/driving force
Fwxti is greater than the maximum regenerative braking force of
each wheel, the electronic controller 16 for controlling driving
force sets the target driving force Fwdti of each wheel to zero,
sets the target regenerative braking force Fwrti of each wheel to
the maximum regenerative braking force Fwxrimax (i=fl, fr, rl, rr),
and controls the electric motor generators 12FL to 12RR such that
the regenerative braking force becomes the maximum regenerative
braking force Fwxrimax. Further, it calculates the braking force
that corresponds to the difference between the target
braking/driving force Fwxti and the maximum regenerative braking
force Fwxrimax as the target friction braking force Fwbti (i=fl,
fr, rl, rr), and outputs the signals indicating the target friction
braking forces Fwbti of the wheels to the electronic controller 28
for controlling braking force.
[0078] The electronic controller 28 for controlling braking force
calculates the target braking pressure Pbti (i=fl, fr, rl, rr) of
each wheel on the basis of the target friction braking force Fwbti
of each wheel inputted from the electronic controller 16 for
controlling driving force, and controls the hydraulic circuit 20
such that the braking pressure Pbi of each wheel becomes the
associated target braking pressure Pbti, and the friction braking
force Fwbi (i=fl, fr, rl, rr) of each wheel thereby becomes the
associated target friction braking force Fwbti of each wheel.
[0079] The braking/driving force control achieved by the electronic
controller 16 for controlling driving force in the first embodiment
will now be explained with reference to the flowchart shown in FIG.
3. The control by the flowchart shown in FIG. 3 is started by the
activation of the electronic controller 16 for controlling driving
force, and it is repeatedly executed every predetermined time until
an ignition switch, not shown, is turned off.
[0080] At Step 10, the signals indicating the accelerator opening
.phi. detected by the accelerator opening sensor 14 and the like
are firstly read. At Step 20, the vehicle target braking/driving
force Fvn and vehicle target yaw moment Mvn that are required to
the vehicle and caused by the control of the braking/driving force
of each wheel are calculated in the aforesaid manner on the basis
of the accelerator opening .phi. and the like.
[0081] At Step 30, the vehicle maximum driving force Fvdmax,
vehicle maximum braking force Fvbmax, vehicle maximum yaw moment
Mvimax in the leftward turning direction, and vehicle maximum yaw
moment Mvrmax in the rightward direction, attainable by the
braking/driving force of each wheel, are calculated by maps or
functions, not shown, on the basis of the road friction coefficient
.mu.. Specifically, the points A to D shown in FIG. 4 are
specified.
[0082] At Step 40, it is determined whether or not the absolute
value of the target braking/driving force Fvn is not more than the
vehicle maximum driving force Fvdmax and the absolute value of the
vehicle target yaw moment Mvn is not more than the vehicle maximum
yaw moment Mvimax, i.e., it is determined whether the vehicle
target braking/driving force Fvn and the vehicle target yaw moment
Mvn are within the range of the quadrangular 100 or not and the
target braking/driving force Fvn and the target yaw moment Mvn can
be achieved or not through the control of the braking/driving force
of each wheel. When the negative determination is made, the program
proceeds to Step 60. When the positive determination is made, the
vehicle target braking/driving force Fvt and the vehicle target yaw
moment Mvt after the modification are respectively set to the
target braking/driving force Fvn and the target yaw moment Mvn at
Step 50, and then, the program proceeds to Step 200.
[0083] At Step 60, the neural network 50 calculates the
distribution ratio K in such a manner that, as the acceleration
opening .phi., the rate of change of the acceleration opening
.phi.d, the master cylinder pressure Pm, the rate of change of the
master cylinder pressure Pmd which indicate a condition of an
acceleration or deceleration operation by a driver are great, the
distribution ratio K becomes a small value, and as the magnitude of
the steering angle .theta. and/or the magnitude of the rate of
change of the steering angle .phi.d which indicate a condition of
steering by a driver are great, the distribution ratio K becomes a
great value.
[0084] At Step 80, the straight line L, which is the closest to the
point P indicating the vehicle target braking/driving force Fvn and
the vehicle target yaw moment Mvn, is specified among the outer
lines of the quadrangle 100, as shown in FIG. 5. The straight line
L is specified to be the segment AC when the point P that indicates
the vehicle target braking/driving force Fvn and the vehicle target
yaw moment Mvn is in the first quadrant in FIG. 4A, specified to be
the segment BC when the point P is in the second quadrant in FIG.
4A, specified to be the segment BD when the point P is in the third
quadrant in FIG. 4A, and specified to be the segment AD when the
point P is in the fourth quadrant in FIG. 4A.
[0085] The coordinate at the end Q1 of the straight line L where
the magnitude of the yaw moment is greater is defined as (Mvmax,
0), and the coordinate at the end Q2 where the magnitude of the yaw
moment is smaller is defined as (0, Fvmax). At Step 90, the vector
component (Zx1 Zy1) from the point P to the end Q1 and the vector
component (Zx2 Zy2) from the point P to the end Q2 are calculated
in accordance with the following equations 4 and 5, respectively.
The ends Q1 and Q2 are the points C and t A, respectively when the
point P is in the first quadrant in FIG. 4A, the points C and B,
respectively when the point P is in the second quadrant in FIG. 4A,
the points D and t A, respectively when the point P is in the third
quadrant in FIG. 4A, and the points D and B, respectively when the
point P is in the fourth quadrant in FIG. 4A.
(Zx1 Zy1)=(-Fvn Mvmax-Mvn) (4)
(Zx2 Zy2)=(Fvmax-Fvn-Mvn) (5)
[0086] At Step 100, the vehicle target braking/driving force Fvt
after the modification and the vehicle target yaw moment Mvt after
the modification are calculated as the values of the coordinate at
the target point R, which is the internally dividing point of the
straight line L based upon the distribution ratio K, in accordance
with the equations 6 and 7 described below. Thereafter, the program
proceeds to Step 200.
Fvt=Fvn+K(Fvmax-Fvn)+(1-K)(-Mvn) (6)
Mvt=Mvn+K(-Fvn)+(1-K)(Mvmax-Mvn) (7)
[0087] At Step 200, the target braking/driving force Fwxti (i=fl,
fr, rl, rr) of each wheel to achieve the target braking/driving
force Fvt and the target yaw moment Mvt is calculated in the
above-mentioned manner on the basis of the vehicle target
braking/driving force Fvt after the modification and the vehicle
target yaw moment Mvt after the modification.
[0088] At Step 210, the target friction braking force Fwbti is
calculated in the aforesaid manner, and the signals indicating the
target friction braking forces Fwbti are outputted to the
electronic controller 28 for controlling braking force, whereby the
electronic controller 28 for controlling braking force makes a
control such that the friction braking force Fwbi of each wheel
becomes the associated target friction braking force Fwbti.
[0089] At Step 220, each of the electric motor generators 12FL to
12RR is controlled such that the driving force Fwdi or the
regenerative braking force Fwri of each wheel respectively becomes
the target driving force Fwdti or the target regenerative braking
force Fwrti.
[0090] According to the illustrated first embodiment, the vehicle
target braking/driving force Fvn and the vehicle target yaw moment
Mvn, required to the vehicle, through the control of the
braking/driving forces of the wheels are calculated at Step 20, the
vehicle maximum driving force Fvdmax, vehicle maximum braking force
Fvbmax, vehicle maximum yaw moment Mvlmax in the leftward turning
direction, and the vehicle maximum yaw moment Mvrmax in the
rightward turning direction, those of which are attainable by the
braking/driving forces of the wheels, are calculated at Step 30,
and it is determined at Step 40 whether or not the target
braking/driving force Fvn and the target yaw moment Mvn can be
achieved or not through the control of the braking/driving forces
of the wheels.
[0091] When it is determined at Step 40 that the target
braking/driving force Fvn and the target yaw moment Mvn cannot be
attained through the control of the braking/driving forces of the
wheels, the distribution ratio K is calculated at Step 60 by the
neural network 50 in such a manner that, as the value indicating
the condition of the acceleration or deceleration operation by a
driver is great, the distribution ratio K becomes a small value,
and as the value indicating the condition of the steering operation
by a driver is great, the distribution ratio K becomes a great
value. At Step 80, the straight line L, which is the closest to the
point P indicating the vehicle target braking/driving force Fvn and
the vehicle target yaw moment Mvn, is specified among the outer
lines of the quadrangle 100. At Steps 90 and 100, the value of the
coordinate at the target point R, which is the internally dividing
point of the straight line L based upon the distribution ratio K,
is calculated as the vehicle target braking/driving force Fvt after
the modification and the vehicle target yaw moment Mvt after the
modification.
[0092] Consequently, according to the illustrated first embodiment,
when the vehicle is under the condition where the target
braking/driving force Fvn and the target yaw moment Mvn cannot be
achieved by the control of the braking/driving forces of the
wheels, the distribution ratio K is calculated in such a manner
that, as the value indicating the condition of the acceleration or
deceleration operation by a driver is great, the distribution ratio
K becomes a small value, and as the value indicating the condition
of the steering operation by a driver is great, the distribution
ratio K becomes a great value. Further, the straight line L, which
is the closest to the point P indicating the vehicle target
braking/driving force Fvn and the vehicle target yaw moment Mvn, is
specified among the outer lines of the quadrangle 100. Then, the
value of the coordinate at the target point R, which is the
internally dividing point of the straight line L based upon the
distribution ratio K, is calculated as the vehicle target
braking/driving force Fvt after the modification and the vehicle
target yaw moment Mvt after the modification. As a result, the
braking/driving force and the yaw moment, which are as closer to
the braking/driving force and the yaw moment required to the
vehicle as possible and are suitable for the condition of a driving
operation by a driver, can be achieved within the ranges of the
braking/driving forces that can be generated by the wheels.
[0093] In particular, in the illustrated first embodiment, the
driving sources for the wheels are electric motor generators 12FL
to 12RR provided on each wheel. In case where the target
braking/driving forces Fwxti of the wheels take negative values,
which means the target braking/driving forces Fwxti are braking
forces, the regenerative braking forces by the electric motor
generators 12FL to 12RR are used. Accordingly, the vehicle motion
energy can effectively be returned as electric energy upon the
braking operation for deceleration, while achieving the
braking/driving force and the yaw moment required to the vehicle as
much as possible within the range of the braking/driving forces
that can be generated by the wheels.
[0094] While, in the illustrated first embodiment, the electric
motor generators 12FL to 12RR are in-wheel motors, the electric
motor generators may be provided at the vehicle body. Further, the
electric motor generators as driving sources for wheels may not
perform regenerative braking. The driving source may be other than
the electric motor generator so long as it can increase or decrease
the driving force of each wheel independently. The same is true for
a third embodiment described later.
[0095] Although the electric motor generators 12FL to 12RR are
provided so as to correspond to four wheels in the illustrated
first embodiment, this embodiment may be applied to a vehicle
having driving sources provided only at the left and right front
wheels or left and right rear wheels. In this case, the quadrangle
100 takes a form shown by 100' in FIG. 4C, and when the vehicle yaw
moment in the leftward turning direction and the vehicle yaw moment
in the rightward turning direction are the maximum values Mvlmax
and Mvrmax respectively, the vehicle braking/driving force takes a
negative value, which means that the vehicle braking/driving force
is a braking force. The above-mentioned effects can also be
achieved with this vehicle.
Second Embodiment
[0096] FIG. 7 is a schematic block diagram showing a
braking/driving force control apparatus applied to a
four-wheel-drive vehicle in which driving force and regenerative
braking force from a single electric motor generator, which is
common to four wheels, are controlled so as to be distributed to
front and rear wheels and right and left wheels according to a
second embodiment of the present invention. The components in FIG.
7 same as those in FIG. 1 are identified by the same numerals in
FIG. 1.
[0097] In this second embodiment, an electric motor generator 40 is
provided that serves as a driving source common to the front left
wheel 10FL, front right wheel 10FR, rear left wheel 10RL, and rear
right wheel 10RR. The driving force or the regenerative braking
force from the electric motor generator 40 is transmitted to a
front-wheel propeller shaft 44 and rear-wheel propeller shaft 46
through a center differential 42 that can control the distribution
ratio to the front wheels and rear wheels.
[0098] The driving force or the regenerative braking force of the
front-wheel propeller shaft 44 is transmitted to the front-left
wheel axle 50L and front-right wheel axle 50R by a front-wheel
differential 48 that can control the distribution ratio to the
front-left wheel and front-right wheel, whereby the front-left
wheel 10FL and front-right wheel 10FR are rotatably driven.
Similarly, the driving force or the regenerative braking force of
the rear-wheel propeller shaft 46 is transmitted to the rear-left
wheel axle 54L and rear-right wheel axle 54R by a rear-wheel
differential 52 that can control the distribution ratio of the
rear-left wheel and rear-right wheel, whereby the rear-left wheel
10RL and rear-right wheel 10RR are rotatably driven.
[0099] The driving force of the electric motor generator 40 is
controlled by the electronic controller 16 for controlling driving
force on the basis of the accelerator opening .phi. detected by the
accelerator opening sensor 14. The regenerative braking force of
the electric motor generator 40 is also controlled by the
electronic controller 16 for controlling driving force. The
electronic controller 16 for controlling driving force controls the
distribution ratio of the driving force and regenerative braking
force to the front wheels and rear wheels by the center
differential 42, controls the distribution ratio of the driving
force and regenerative braking force to the left wheels and right
wheels by the front-wheel differential 48, and controls the
distribution ratio of the driving force and regenerative braking
force to the left wheels and right wheels by the rear-wheel
differential 52.
[0100] In this second embodiment too, the electronic controller 16
for controlling driving force calculates, in the same manner as in
the first embodiment, the target braking/driving force Fvn,
required to the vehicle, through the control of the braking/driving
force of each wheel, the vehicle target yaw moment Mvn, required to
the vehicle, through the control of the braking/driving force of
each wheel, the vehicle maximum driving force Fvdmax, the vehicle
maximum braking force Fvbmax, the vehicle maximum yaw moment Mvimax
in the leftward turning direction, and the vehicle maximum yaw
moment Mvrmax in the rightward turning direction by the
braking/driving force of each wheel.
[0101] In the illustrated second embodiment, it is assumed that the
driving forces Fwdi of the wheels when the maximum driving force of
the electric motor generator 40 is uniformly distributed to the
front-left wheel 10FL, front-right wheel 10FR, rear-left wheel 10RL
and rear-right wheel 10RR is smaller than the producible maximum
longitudinal force that is determined by the friction coefficient
.mu. of the normal road surface.
[0102] As shown in FIG. 8A, the vehicle maximum driving force
Fvdmax under the condition where the yaw moment by the
braking/driving forces of the wheels is not acted on the vehicle is
achieved when the braking/driving forces Fwxfl and Fwxfr of the
front-left wheel 10FL and front-right wheel 10FR are the maximum
driving forces Fwdflmax and Fwdformax in case where the
distribution of the driving force to the right and left wheels is
equal, and the braking/driving forces Fwxrl and Fwxrr of the
rear-left wheel 10RL and rear-right wheel 10RR are the maximum
driving forces Fwdrlmax and Fwdrrmax in case where the distribution
of the driving force to the right and left wheels is equal.
[0103] Similarly, as shown in FIG. 8B, the vehicle maximum braking
force Fvbmax under the condition where the yaw moment by the
braking/driving force of the wheels is not acted on the vehicle is
achieved when the braking/driving forces Fwxfl and Fwxfr of the
front-left wheel 10FL and front-right wheel 10FR are the maximum
braking forces Fwbflmax and Fwbformax in case where the
distribution of the braking force to the right and left wheels is
equal, and the braking/driving forces Fwxrl and Fwxrr of the
rear-left wheel 10RL and rear-right wheel 10RR are the maximum
braking forces Fwbrlmax and Fwbrrmax in case where the distribution
of the braking force to the right and left wheels is equal.
[0104] As shown in FIG. 8C, the vehicle maximum yaw moment Mvimax
in the leftward turning direction under the condition where the
longitudinal force by the braking/driving forces of the wheels is
not acted on the vehicle is achieved in case where the driving
force is distributed to the right wheels, the braking/driving
forces Fwxfr and Fwxrr of the front-right wheel 10FR and rear-right
wheel 10RR are the maximum driving forces Fwdformax' and Fwdrrmax',
and their magnitudes are equal to the magnitudes of the maximum
braking forces Fwbflmax and Fwbrlmax of the front-left wheel 10FL
and rear-left wheel 10RL respectively.
[0105] As shown in FIG. 8D, the vehicle maximum yaw moment Mvimax'
in the leftward turning direction under the condition where the
vehicle braking/driving force is the maximum driving force Fvdmax
is achieved in case where the braking/driving forces Fwxfl and
Fwxrl of the front-left wheel 10FL and rear-left wheel 10RL are
respectively 0, and the braking/driving forces Fwxfr and Fwxrr of
the front-right wheel 10FR and rear-right wheel 10RR are the
maximum driving forces Fwdflmax' and Fwdrrmax'.
[0106] As shown in FIG. 9E, the vehicle maximum yaw moment Mvimax''
in the leftward turning direction under the condition where the
driving force is not acted on any wheels is achieved in case where
the braking/driving forces Fwxfr and Fwxrr of the front-right wheel
10FR and rear-right wheel 10RR are respectively 0, and the
braking/driving forces Fwxfl and Fwxrl of the front-left wheel 10FL
and rear-left wheel 10RL are the maximum braking forces Fwbfimax
and Fwbrlmax.
[0107] As shown in FIG. 9F, the vehicle maximum yaw moment Mvrmax
in the rightward turning direction under the condition where the
longitudinal force by the braking/driving forces of the wheels is
not acted on the vehicle is achieved in case where the driving
force is distributed to the left wheels, the braking/driving forces
Fwxfl and Fwxrl of the front-left wheel 10FL and rear-left wheel
10RL are the maximum driving forces Fwdflmax' and Fwdrlmax', and
their magnitudes are equal to the magnitudes of the maximum braking
forces Fwbformax and Fwbrrmax of the front-right wheel 10FR and
rear-right wheel 10RR respectively.
[0108] As shown in FIG. 9G, the vehicle maximum yaw moment Mvrmax'
in the rightward turning direction under the condition where the
vehicle braking/driving force is the maximum driving force Fvdmax
is achieved in case where the braking/driving forces Fwxfr and
Fwxrr of the front-right wheel 10FR and rear-right wheel 10RR are
respectively 0, and the braking/driving forces Fwxfl and Fwxrl of
the front-left wheel 10FL and rear-left wheel 10RL are the maximum
driving forces Fwdflmax' and Fwdrlmax'.
[0109] As shown in FIG. 9H, the vehicle maximum yaw moment Mvrmax''
in the rightward turning direction under the condition where the
driving force is not acted on any wheels is achieved in case where
the braking/driving forces Fwxfl and Fwxrl of the front-left wheel
10FL and rear-left wheel 10RL are respectively 0, and the
braking/driving forces Fwxfr and Fwxrr of the front-right wheel
10FR and rear-right wheel 10RR are the maximum braking forces
Fwbformax and Fwbrrmax.
[0110] The maximum driving forces Fwdimax of the wheels are
determined by the maximum output torque of the electric motor
generator 40, the road friction coefficient .mu., and each
distribution ratio, and the maximum braking forces Fwbimax of the
wheels are determined by the road friction coefficient .mu..
Therefore, the vehicle maximum driving force Fvdmax, vehicle
maximum braking force Fvbmax, vehicle maximum yaw moment Mvlmax in
the leftward turning direction, and vehicle maximum yaw moment
Mvrmax in the rightward turning direction are also determined by
the maximum output torque of the electric motor generator 40 and
the road friction coefficient .mu.. Accordingly, if the maximum
output torque of the electric motor generator 40 and the road
friction coefficient .mu. are found, the vehicle maximum driving
force Fvdmax and the other values can be estimated.
[0111] As shown in FIG. 11A, in a rectangular coordinate with the
vehicle braking/driving force Fvx as abscissa and the vehicle yaw
moment Mv as ordinate, the vehicle braking/driving force Fvx and
the vehicle yaw moment Mv that are attainable by the control of the
braking/driving force of each wheel take values within a hexagon
102 decided by the vehicle maximum driving force Fvdmax, vehicle
maximum braking force Fvbmax, vehicle maximum yaw moment Mvimax in
the leftward turning direction, vehicle maximum yaw moment Mvrmax
in the rightward turning direction, and the variable range of the
vehicle yaw moment Mv when vehicle braking/driving force Fvx are
the maximum driving force Fvdmax or maximum braking force
Fvbmax.
[0112] Notably, in FIG. 11, points A to H correspond to the cases A
to H in FIGS. 8 and 9. As shown by a broken line in FIG. 11A, the
hexagon 102 becomes small as the road friction coefficient .mu.
decreases. Further, as the magnitude of the steering angle .theta.
increases, the lateral force of front left and front right wheels,
that are steerable wheels, increases, so that the allowance of the
longitudinal force becomes small. Therefore, the hexagon 102
becomes small as magnitude of the steering angle .theta.
increases.
[0113] When the output torque of the electric motor generator 40 is
sufficiently great, the maximum driving force and maximum braking
force of each wheel are determined by the road friction coefficient
.mu.. Therefore, supposing that the vehicle accelerating direction
and the vehicle leftward turning direction are defined as positive,
the relationships between the maximum driving force and maximum
braking force of each wheel, the vehicle maximum driving force and
vehicle maximum braking force, and vehicle maximum yaw moment in
the leftward turning direction and vehicle maximum yaw moment in
the rightward turning direction are equal to those in the
above-mentioned first embodiment. Accordingly, the range of the
vehicle driving force and yaw moment that can be achieved by the
braking/driving forces of the wheels becomes the range of the
diamond like the first embodiment.
[0114] Further, when the output torque of the electric motor
generator 40 and the maximum braking force of each wheel are
smaller than those in the embodiment, the vehicle driving force
becomes the maximum even if all the maximum driving force is
distributed to the left wheels or right wheels, and the vehicle
braking force becomes the maximum even if all the braking forces is
distributed to the left wheels or right wheels. Therefore, as
indicated by a phantom line in FIG. 11A, the range of the vehicle
driving force and yaw moment that can be achieved by the
braking/driving forces of the wheels becomes the range of the
rectangle.
[0115] The coordinates at the points A to H shown in FIG. 11 are
(Fvdmax, 0), (Fvbmax, 0), (0, Mvimax), (Fvdmax, KmMvlmax), (Fvbmax,
KmMvimax), (0, Mvrmax), (Fvdmax, -KmMvlmax), and (Fvbmax,
-KmMvlmax), respectively, supposing that the coefficient Km is
defined as not less than 0 and not more than 1.
[0116] Supposing that the longitudinal distribution ratio of the
braking/driving force Fwxi to the rear wheels is defined as Kr
(constant of 0<Kr<1), the lateral distribution ratio of the
braking/driving force Fwxi to the right wheels is defined as Ky
(0.ltoreq.Kr.ltoreq.1) for the front wheels and rear wheels, and
the vehicle tread is defined as Tr, the following equations 8 to 11
are established. Accordingly, the electronic controller 16 for
controlling driving force sets the vehicle target braking/driving
force Fvt and the vehicle target yaw moment Mvt after the
modification by the control of the braking/driving force of each
wheel to the target braking/driving force Fvn and the vehicle
target yaw moment Mvn, when the vehicle target braking/driving
force Fvt and the vehicle target yaw moment Mvt are within the
above-mentioned hexagon 102. For example, it calculates the values
satisfying the following equations 8 to 11 as the target
braking/driving force Fwxti (i=fl, fr, rl, rr) and the lateral
distribution ratio Ky to the right wheels by the least square
method.
Fwxfl+Fwxfr+Fwxrl+Fwxrr=Fvt (8)
{Fwxfr+Fwxrr-(Fwxfl+Fwxrl)}Tr/2=Mvt (9)
(Fwxfl+Fwxfr)Kr=(Fwxrl+Fwxrr)(1-Kr) (10)
(Fwxfl+Fwxrl)Ky=(Fwxfr+Fwxrr)(1-Ky) (11)
[0117] When the vehicle target braking/driving force Fvn and the
vehicle target yaw moment Mvn are outside the range of the
above-mentioned hexagon 102, the electronic controller 16 for
controlling driving force determines whether or not the magnitude
of the target yaw moment Mvn exceeds 0.5 Mvimax. When the magnitude
of the target yaw moment Mvn exceeds 0.5 Mvlmax, the electronic
controller 16 for controlling driving force specifies a straight
line L1, which is the closest to a point P1 indicating the vehicle
target braking/driving force Fvn and the vehicle target yaw moment
Mvn, in the area where the yaw moment is not less than 0.5 Mvlmax
among the outer lines of the hexagon 102 as shown in FIG. 12. Then,
the electronic controller 16 for controlling driving force
calculates a distribution ratio K (a value greater than 0 and less
than 1) for determining an internally dividing point Q1 of the
straight line L in accordance with the operation of the neural
network 50 shown in FIG. 6, whereby the electronic controller 16
for controlling driving force defines the braking/driving force Fv
and the yaw moment Mv at the target point Q1 as the vehicle target
braking/driving force Fvt after the modification and the vehicle
target yaw moment Mvt after the modification, with the internally
dividing point Q1 of the straight line L on the basis of the
distribution ratio K employed as the target point.
[0118] When the magnitude of the target yaw moment Mvn is not more
than 0.5 Mvimax, the electronic controller 16 for controlling
driving force specifies a straight line L2, which is the closest to
a point P2 indicating the vehicle target braking/driving force Fvn
and the vehicle target yaw moment Mvn, in the area where the yaw
moment is not more than 0.5 Mvlmax among the outer lines of the
hexagon 102 as shown in FIG. 13. Then, the electronic controller 16
for controlling driving force calculates a distribution ratio K for
determining an internally dividing point Q2 of the straight line L
in accordance with the operation of the neural network 50 shown in
FIG. 6, whereby the electronic controller 16 for controlling
driving force defines the braking/driving force Fv and the yaw
moment Mv at the target point Q2 as the vehicle target
braking/driving force Fvt after the modification and the vehicle
target yaw moment Mvt after the modification, with the internally
dividing point Q2 of the straight line L on the basis of the
distribution ratio K employed as the target point. Then, the
electronic controller 16 for controlling driving force calculates
the values satisfying the foregoing equations 8 to 11 as the target
braking/driving forces Fwxti of the wheels and the lateral
distribution ratio Ky to the right wheels by the least square
method, for example.
[0119] When the vehicle braking/driving force Fv takes a positive
value which means the vehicle braking/driving force Fv is a driving
force, and the target braking/driving forces Fwxti of the wheels
are positive values that means the braking/driving forces Fwxti are
driving forces, the electronic controller 16 for controlling
driving force sets the target friction braking forces Fwbti and the
target regenerative braking forces Fwrti (i=fl, fr, rl, rr) of the
wheels to zero, outputs the signals indicating the target friction
braking forces Fwbti to the electronic controller 28 for
controlling braking force, and sets the target driving forces Fwdti
(i=fl, fr, rl, rr) of the wheels to the target braking/driving
forces Fwxti.
[0120] Then, the electronic controller 16 for controlling driving
force calculates the target driving current It to the electric
motor generator 40 and the lateral distribution ratio Ky to the
right wheels by unillustrated maps or functions on the basis of the
target driving forces Fwdti, and controls the driving current
applied to the electric motor generator 40 on the basis of the
target driving current It as well as controls the front-wheel
differential 48 and the rear-wheel differential 52 on the basis of
the lateral distribution ratio Ky to the right wheels, thereby
controlling the driving force of each wheel such that the
braking/driving forces Fwxi of the wheels becomes the target
braking/driving force Fwxti.
[0121] On the other hand, when the vehicle braking/driving force Fv
takes a positive value that means the vehicle braking/driving force
Fv is a driving force, but the target braking/driving force Fwxti
of any one of wheels takes a negative value that means it is a
braking force, and when the vehicle braking/driving force Fv takes
a negative value that means it is a braking force, but the target
braking/driving force Fwxti of any one of wheels takes a positive
value that means it is a driving force, the electronic controller
16 for controlling driving force determines the lateral
distribution ratio Ky to the right wheels such that the driving
force is distributed only to the side where the target
braking/driving forces Fwxti take positive values, calculates the
target driving current It to the electric motor generator 40 on the
basis of the sum of the positive target braking/driving forces
Fwxti, and outputs signals indicating the target braking/driving
forces Fwxti to the electronic controller 28 for controlling
braking force such that the friction braking force by the friction
braking device 18 is applied to the wheel having the negative
target braking/driving force Fwxti.
[0122] Then, the electronic controller 16 for controlling driving
force controls the driving current applied to the electric motor
generator 40 on the basis of the target driving current It, and
controls the front-wheel differential 48 and the rear-wheel
differential 52 on the basis of the lateral distribution ratio Ky
to the right wheels. The electronic controller 28 for controlling
braking force applies the friction braking force according to the
target braking/driving force Fwxti to the wheel having the negative
target braking/driving force Fwxti. Accordingly, the
braking/driving forces Fwxi of the wheels are controlled to
coincide with the target braking/driving forces Fwxti.
[0123] When the sum of the target braking/driving forces Fwxti is
not more than the maximum regenerative braking force by the
electric motor generator 40 in case where the vehicle
braking/driving force Fv takes a negative value that means it is a
braking force, and the target braking/driving forces Fwxti of the
wheels take negative values that means they are braking forces, the
electronic controller 16 for controlling driving force sets the
target driving forces Fwdti and the target friction braking forces
Fwbti of the wheels to 0, and sets the target regenerative braking
force Frt to the sum of the target braking/driving forces Fwxti,
thereby controlling the lateral distribution ratio Ky to the right
wheels and the electric motor generator 40 such that the
regenerative braking force becomes the target regenerative braking
force Frt.
[0124] When the magnitude of the target braking/driving force Fwxti
of any one of wheels is greater than the maximum regenerative
braking force by the electric motor generator 40 in case where the
vehicle braking/driving force Fv takes a negative value that means
it is a braking force, and the target braking/driving forces Fwxti
of the wheels take negative values that means they are braking
forces, the electronic controller 16 for controlling driving force
sets the target driving forces Fwdti of the wheels to 0, sets the
regenerative braking force by the electric motor generator 40 to
the maximum regenerative braking force, and sets the lateral
distribution ratio Ky to the right wheels such that the
distribution ratio of the regenerative braking force to the wheel
having the greater target braking/driving force Fwxti
increases.
[0125] Then, the electronic controller 16 for controlling driving
force calculates, as the target friction braking forces Fwbti, the
values obtained by the subtraction from the target braking/driving
forces Fwxti of the wheels the associated regenerative braking
forces of the wheels, and outputs the signals indicating the target
friction braking forces Fwbti to the electronic controller 28 for
controlling braking force. Further, the electronic controller 16
for controlling driving force controls the electric motor generator
40 such that the regenerative braking force becomes the maximum
regenerative braking force, and controls the front-wheel
differential 48 and the rear-wheel differential 52 on the basis of
the lateral distribution ratio Ky to the right wheels.
[0126] In this second embodiment too, the electronic controller 28
for controlling braking force calculates the target braking
pressures Pbti (i=fl, fr, rl, rr) of the wheels on the basis of the
target friction braking forces Fwbti of the wheels inputted from
the electronic controller 16 for controlling driving force, and
controls the hydraulic circuit 20 such that the braking pressures
Pbi of the wheels becomes the associated target braking pressures
Pbti, thereby controlling such that the friction braking forces
Fwbi (i=fl, fr, rl, rr) of the wheels become the associated target
friction braking forces Fwbti of the wheels.
[0127] The braking/driving force control in the second embodiment
will now be explained with reference to the flowchart shown in FIG.
10. Steps in FIG. 10 same as Steps shown in FIG. 3 are identified
by the same numbers. The control by the flowchart shown in FIG. 10
is started by the activation of the electronic controller 16 for
controlling driving force, and it is repeatedly executed every
predetermined time until an ignition switch, not shown, is turned
off.
[0128] In this second embodiment, Steps 10 to 60 and Steps 200 to
220 are executed in the same manner as in the first embodiment. It
is determined at Step 70, which is executed after Step 60, whether
or not the absolute value of the target yaw moment exceeds 0.5
Mvlmax. When a negative determination is made, the program proceeds
to Step 110, and when a positive determination is made, the program
proceeds to Step 80.
[0129] At Steps 80 to 100, the processes same as those at Steps 80
to 100 in the above-described first embodiment are executed, except
that the point P is the point P1, the straight line L is the
straight line L1, and the internally dividing point R of the
straight line L based upon the distribution ratio K is the
internally dividing point R1 of the straight line L1 based upon the
distribution ratio K. The ends Q1 and Q1 are the points C and D,
respectively when the point P is in the first quadrant in FIG. 11,
the points C and E, respectively when the point P is in the second
quadrant in FIG. 11, the points F and H, respectively when the
point P is in the third quadrant in FIG. 11, and the points F and
G, respectively when the point P is in the fourth quadrant in FIG.
11.
[0130] At Step 110, a straight line L2, which is the closest to a
point P2 indicating the vehicle target braking/driving force Fvn
and the vehicle target yaw moment Mvn, is specified among the outer
lines of the hexagon 102 as shown in FIG. 13. The straight line L2
is specified to be the segment AD when the point P is in the first
quadrant in FIG. 11, the segment BE when the point P is in the
second quadrant in FIG. 11, the segment BH when the point P is in
the third quadrant in FIG. 11, and the segment AG when the point P
is in the fourth quadrant in FIG. 11.
[0131] The coordinate at the end Q1 of the straight line L2 where
the magnitude of the yaw moment is greater is defined as (Fvmax,
0.5Mvmax), and the coordinate at the end Q2 where the magnitude of
the yaw moment is smaller is defined as (Fvmax, 0). At Step 120,
the vector component (Zx1 Zy1) from the point P to the end Q1 and
the vector component (Zx2 Zy2) from the point P to the end Q2 are
calculated in accordance with the following equations 12 and 13,
respectively.
(Zx1 Zy1)=(Fvmax-Fvn 0.5Mvmax-Mvn) (12)
(Zx2 Zy2)=(Fvmax-Fvn-Mvn) (13)
[0132] The ends Q1 and Q2 are the points D and A, respectively when
the point P is in the first quadrant in FIG. 11, the points E and
B, respectively when the point P is in the second quadrant in FIG.
11, the points H and B, respectively when the point P is in the
third quadrant in FIG. 11, and the points G and A, respectively
when the point P is in the fourth quadrant in FIG. 11. Further,
Mvmax is Mvlmax when the point P is in the first or second quadrant
in FIG. 11, while Mvmax is Mvrmax when the point P is in the third
or fourth quadrant in FIG. 11.
[0133] At Step 130, the vehicle target braking/driving force Fvt
after the modification and the vehicle target yaw moment Mvt after
the modification are calculated as the value of the coordinate at
the target point R2, which is the internally dividing point of the
straight line L2 based upon the distribution ratio K, in accordance
with the equations 14 and 15 described below. Thereafter, the
program proceeds to Step 200.
Fvt=Fvn+K(Fvmax-Fvn)+(1-K)(-Mvn) (14)
Mvt=Mvn+K(Fvmax-Fvn)+(1-K)(0.5Mvmax-Mvn) (15)
[0134] The control same as that in the above-mentioned first
embodiment is executed at Step 210 in this second embodiment,
except that the target regenerative braking force Frt and the
target friction braking forces Fwbti of the wheels are calculated
as described above.
[0135] Thus, according to the illustrated second embodiment, when
the target braking/driving force Fvn and the target yaw moment Mvn
cannot be achieved by the control of the braking/driving forces of
the wheels, Steps 70 to 130 are executed, whereby the straight line
L1 or L2, which is the closest to the point P1 or P2 indicating the
vehicle target braking/driving force Fvn and the vehicle target yaw
moment Mvn, is specified among the outer lines of the hexagon 102.
Then, the value of the coordinate at the target point R1 or R2,
which is the internally dividing point of the straight line L1 or
L2 based upon the distribution ratio K, is calculated as the
vehicle target braking/driving force Fvt after the modification and
the vehicle target yaw moment Mvt after the modification.
[0136] Consequently, according to the illustrated second
embodiment, when the vehicle, in which right and left wheels are
braked and driven by an electric motor generator common to these
wheels, and driving force and regenerative braking force are
controlled so as to be distributed to I right and left wheels, is
under the condition where the target braking/driving force Fvn and
the target yaw moment Mvn cannot be achieved by the control of the
braking/driving forces of the wheels, the braking/driving force and
the yaw moment, which is as closer to the braking/driving force and
the yaw moment required to the vehicle as possible and is suitable
for the condition of a driving operation by a driver, can be
achieved within the ranges of the braking/driving forces that can
be generated by the wheels.
[0137] According to the illustrated second embodiment, in
particular, the electric motor generator 40 that is common to all
the wheels and serves as a driving source generates a regenerative
braking force, in case where the vehicle target braking/driving
force Fvt takes a negative value that means it is a braking force.
Therefore, like the above-mentioned first embodiment, the vehicle
motion energy can effectively be returned as electric energy upon
the braking operation for deceleration, while achieving the
braking/driving force and the yaw moment required to the vehicle as
much as possible within the range of the braking/driving force that
can be generated by each wheel.
[0138] According to the illustrated first and second embodiments,
the vehicle target longitudinal acceleration Gxt is calculated on
the basis of the accelerator opening .phi. and the master cylinder
pressure Pm that indicate the amount of acceleration or
deceleration operation by a driver, the vehicle target yaw rate
.gamma.t is calculated on the basis of the steering angle .theta.,
which is a steering operation amount by a driver, and the vehicle
speed V, the target barking/driving force Fvn required to the
vehicle is calculated on the basis of the vehicle target
longitudinal acceleration Gxt, and the target total yaw moment Mvnt
required to the vehicle is calculated on the basis of the vehicle
target yaw moment .gamma.t.
[0139] The vehicle turning yaw moment Ms by the lateral force of
each wheel is calculated, and the value obtained by subtracting the
turning yaw moment Ms from the vehicle target total yaw moment Mvnt
is calculated as the vehicle target yaw moment Mvn, which is
required to the vehicle and is to be attained by the control of the
braking/driving force of each wheel. Therefore, the vehicle target
yaw moment required to the vehicle to be attained by the control of
the braking/driving force of each wheel can be surely and correctly
calculated in just proportion, compared to the case where the
vehicle turning yaw moment Ms attained by the lateral forces of the
wheels is not considered.
[0140] Although the driving source is the electric motor generator
40 that is common to four wheels in the illustrated second
embodiment, the driving source for driving the wheels so as to
execute the control of the driving force distribution between left
and right wheels may be optional driving means known by a person
skilled in the art, such as an internal combustion engine, hybrid
system, or the like. The same is true for a fourth embodiment
described later.
[0141] Although a single electric motor generator 40 is provided as
a common driving source to four wheels in the illustrated second
embodiment, a driving source common to the front-left wheel and
front-right wheel and a driving source common to the rear-left
wheel and rear-right wheel may be provided. Further, a driving
source common to only the front-left wheel and front-right wheel or
a driving source common to only the rear-left wheel and rear-right
wheel may be provided. In this case, the hexagon 102 takes a shape
102' shown in FIG. 11B. Specifically, when the vehicle yaw moment
in the leftward turning direction and the vehicle yaw moment in the
rightward turning direction are the maximum values Mvimax and
Mvrmax respectively, the vehicle braking/driving force takes a
negative value, which means that the vehicle braking/driving force
is a braking force. The above-mentioned effects can also be
achieved by this vehicle. The same is true for the later-described
fourth embodiment.
Third Embodiment
[0142] FIG. 14 is a flowchart showing an main part of a
braking/driving force control routine in a third embodiment of a
vehicle braking/driving force control apparatus that is applied to
a four-wheel-drive vehicle of a wheel-in-motor type and is made as
an modified example of the first embodiment. Steps in FIG. 14 same
as Steps shown in FIG. 3 are identified by the same numbers in FIG.
3.
[0143] In this third embodiment, the areas which are between
straight lines perpendicular to the straight lines at both sides of
the apexes A to D of the outer lines of the quadrangle 100, which
indicates the range of the vehicle braking/driving force Fvx and
the vehicle yaw moment Mv that are attainable through the control
of the braking/driving forces of the wheels, are defined as S1 to
S4 as shown in FIG. 15. When the vehicle target braking/driving
force Fvn and the vehicle target yaw moment Mvn are in one of the
areas S1 to S4, the braking/driving force Fv and the yaw moment Mv
at the target point R are not defined as the vehicle target
braking/driving force Fvt after the modification and the vehicle
target yaw moment Mvt after the modification with the internally
dividing point R of the straight line L based upon the distribution
ratio K employed as the target point, but the values of the
corresponding apex are defined as the vehicle target
braking/driving force Fvt after the modification and the vehicle
target yaw moment Mvt after the modification.
[0144] Accordingly, as shown in FIG. 14, at Step 51 that is
executed before Step 60, it is determined whether or not the
vehicle target braking/driving force Fvn and the vehicle target yaw
moment Mvn are in the non-distribution area, i.e., one of the areas
S1 to S4. When a negative determination is made, the program
proceeds to Step 60, while when a positive determination is made,
the program proceeds to Step 52.
[0145] At Step 52, it is determined whether or not the absolute
value of the vehicle target braking/driving force Fvn is greater
than the vehicle maximum driving force Fvdmax. When a negative
determination is made, the vehicle target braking/driving force Fvt
after the modification is set to 0, and the vehicle target yaw
moment Mvt is set to Mvmax at Step 53. When a positive
determination is made, the target braking/driving force Fvt after
the modification is set to Fvmax, and the vehicle target yaw moment
Mvt after the modification is set to 0. In this case, Mvmax is set
to Mvimax when the vehicle target yaw moment Mvn assumes a positive
value, while it is set to Mvrmax when the vehicle target yaw moment
assumes a negative value. Further, Fvmax is set to Fvdmax when the
vehicle target braking/driving force Fvn assumes a positive value,
while it is set to Fvbmax when the vehicle target braking/driving
force Fvn assumes a negative value.
[0146] Thus, according to the illustrated third embodiment, the
operation and effect similar to those in the first embodiment can
be obtained, and additionally, under the condition where the
magnitude of the vehicle target braking/driving force Fvn and/or
the magnitude of the vehicle target yaw moment Mvn is great, the
driving force and yaw moment required to the vehicle can surely be
achieved compared to the above-described first embodiment.
Fourth Embodiment
[0147] FIG. 16 is a flowchart showing an main part of a
braking/driving force control routine in a fourth embodiment of a
vehicle braking/driving force control apparatus that is applied to
a four-wheel-drive vehicle, in which driving force and regenerative
braking force from a single electric motor generator that is common
to four wheels are controlled so as to be distributed to front and
rear wheels and right and left wheels and is made as an modified
example of the second embodiment. Steps in FIG. 16 same as Steps
shown in FIG. 14 are identified by the same numbers in FIG. 14.
[0148] In this fourth embodiment, the areas which are between
straight lines perpendicular to the straight lines at both sides of
the apexes A to H of the outer lines of the hexagon 102, which
indicates the range of the vehicle braking/driving force Fvx and
the vehicle yaw moment Mv that are attainable through the control
of the braking/driving forces of the wheels, are defined as S1 to
S6 as shown in FIG. 17. When the vehicle target braking/driving
force Fvn and the vehicle target yaw moment Mvn are in one of the
areas S1 to S6, the braking/driving force Fv and the yaw moment Mv
at the target point R1 or R2 are not defined as the vehicle target
braking/driving force Fvt after the modification and the vehicle
target yaw moment Mvt after the modification with the internally
dividing point R1 or R2 of the straight line L1 or L2 based upon
the distribution ratio K employed as the target point, but the
values of the corresponding apex are defined as the vehicle target
braking/driving force Fvt after the modification and the vehicle
target yaw moment Mvt after the modification.
[0149] Accordingly, as shown in FIG. 16, at Step 51 that is
executed before Step 60, it is determined whether or not the
vehicle target braking/driving force Fvn and the vehicle target yaw
moment Mvn are in the non-distribution area, i.e., one of the areas
S1 to S6. When a negative determination is made, the program
proceeds to Step 60, while when a positive determination is made,
the program proceeds to Step 52.
[0150] Step 52 and Step 53 are executed in the same manner as in
the third embodiment. When a positive determination is made at Step
52, the vehicle target braking/driving force Fvt after the
modification is set to Fvmax, and the vehicle target yaw moment Mvt
is set to 0.5Mvmax at Step 55. In this case, Mvmax is set to Mvimax
when the vehicle target yaw moment Mvn assumes a positive value,
while it is set to Mvrmax when the vehicle target yaw moment
assumes a negative value. Further, Fvmax is set to Fvdmax when the
vehicle target braking/driving force Fvn assumes a positive value,
while it is set to Fvbmax when the vehicle target braking/driving
force Fvn assumes a negative value.
[0151] Thus, according to the illustrated fourth embodiment, the
operation and effect similar to those in the second embodiment can
be obtained, and additionally, like the above-described third
embodiment, under the condition where the magnitude of the vehicle
target braking/driving force Fvn or the magnitude of the vehicle
target yaw moment Mvn is great, the driving force and yaw moment
required to the vehicle can surely be achieved compared to the
above-described second embodiment.
[0152] The present invention is explained in detail with respect to
specific embodiments, but the invention is not limited to the
above-mentioned embodiments. It would be apparent for a person
skilled in the art that various other modifications are possible
within the scope of the present invention.
[0153] For example, although the regenerative braking force is
generated according to need by the electric motor generators 12FL
to 12RR and the electric motor generator 40 in the aforesaid first
to fourth embodiments, it may be revised such that the regenerative
braking is not performed, even if the driving source is an electric
motor generator, and the braking force is generated only by the
friction braking.
[0154] The longitudinal distribution ratio Kr of the
braking/driving force to the rear wheels is constant in the
aforesaid first to fourth embodiments. However, the longitudinal
distribution ratio Kr to the rear wheels may be variably set in
accordance with the magnitude of the steering angle such that the
longitudinal distribution ratio Kr to the rear wheels gradually
increases as the magnitude of the steering angle increases, since
in general, the lateral force of the steerable wheel increases and
the allowable longitudinal force of the steerable wheel decreases
as the magnitude of the steering angle increases.
[0155] In general, as the braking forces of the rear wheels
increase upon the braking of the vehicle for deceleration, the
lateral force of the rear wheels decreases to thereby deteriorate
the running stability of the vehicle. Therefore, the longitudinal
distribution ratio Kr to the rear wheels may be variably set in
accordance with the vehicle target braking/driving force such that
it decreases as the vehicle target braking/driving force takes a
negative value and its magnitude is greater.
[0156] In the above-described first to fourth embodiments, when the
vehicle target braking/driving force Fvn and/or the vehicle target
yaw moment Mvn are outside the range of the quadrangle 100 or
hexagon 102 indicating the vehicle target braking/driving force Fvn
and the vehicle target yaw moment Mvn that are attainable by the
braking/driving forces of the wheels, the straight line L closest
to the point P indicating the vehicle target braking/driving force
Fvn and the vehicle target yaw moment Mvn is specified among the
outer lines. The internally dividing point R on the basis of the
distribution ratio K is obtained to the whole of the straight line
L. The value at the internally dividing point R is defined as the
vehicle target braking/driving force Fvt after the modification and
the vehicle target yaw moment Mvt after the modification. However,
as shown in FIG. 18, for example, when the magnitude of the vehicle
target braking/driving force Fvn or the magnitude of the vehicle
target yaw moment Mvn exceeds the maximum value Fvmax of the
braking/driving force and the maximum value Mvmax of the yaw moment
respectively, the straight line L may be specified for the range
that is not more than the magnitude of the vehicle target
braking/driving force Fvn or the magnitude of the vehicle target
yaw moment, and the internally dividing point R based upon the
distribution ratio K may be obtained for the straight line L.
[0157] In the aforesaid first to fourth embodiments, the target
braking/driving force Fvn and the target yaw moment Mvn by the
control of the braking/driving force of each wheel required to the
vehicle are calculated on the basis of the amount of the
acceleration or deceleration operation and the amount of the
steering operation by the driver. However, in case where the
vehicle behavior is unstable, the target braking/driving force Fvn
and the target yaw moment Mvn may be corrected so as to be
calculated by considering the target longitudinal acceleration or
target yaw rate, which are required to stabilize the behavior of
the vehicle, in addition to the amount of the acceleration or
deceleration operation and the amount of the steering operation by
the driver.
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